Rotating spindles for tool holders have taken many forms. U.S. Pat. No. 2,957,393 discloses a frictional clamp on a rotary spindle. U.S. Pat. No. 3,397,614 discloses a piston surrounding a collet which moves axially to clamp a spindle to a quill. U.S. Pat. No. 4,051,583 discloses a turret with plural spindles, each of which can be oriented in a particular angular position. U.S. Pat. No. 4,570,313 discloses a spindle which may be rotatable or which may be locked against rotation by interengagement of three sets of teeth. U.S. Pat. 4,643,623 discloses a claw clutch which is engaged when the tool holder is not in the spindle and disengaged when inserted in the spindle so it is free to rotate. In U.S. Pat. No. 4,570,313, when the spindle is clamped against rotation, any vibration of the tool in the tool spindle mount as the tool works on a workpiece will be transmitted to the ball bearings despite the presence of the interlocking gear teeth. This can have a damaging effect on the bearings because there is no rolling contact at that time, and such vibration would tend to Brinell the surface of the bearing races.